Just digging through some Gun Digest books I have, in an article by Sam Fadala, it looks like the load I built should be less than 5000 PSI. The similar load in the article using 82grns of FFFg (3F) which is hotter with a faster burn rate and sharper pressure curve and 1+1/8oz shot is actually listed at only 4900 PSI.
I suspect my 80grn charge (of slower burning) FFg (2F) will be a very easy, moderate pressure load with only 1.0 ounce of shot